Method of testing a metallic sample



1953 M. L. YEATER METHOD OF TESTING A METALLIC SAMPLE Filed March 18, 1946 R-F POWER SOURCE VACUUM PUMP INVENTOR. MAX L. YEATER ATTORNEY Patented Oct. 20, 1953 METHOD OF TESTING A METALLIC SAMPLE Max L. Yeater, Boulder, 0010., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application March 18, 1946, Serial No. 655,308

Claims. 1

This invention relates to a method of and system for testing metals and more particularly to a method of and system for determining the presence of occluded impurities in metals by means of atomic hydrogen bombardment.

Heretofore methods of and systems for testing for the presence of occluded impurities in metals were known but were time consuming and laborious. In some cases some impurities would even escape detection by other methods. The method of this invention is applicable to any substance which will combine with hydrogen to form a volatile compound. Certain of the impurities which may reside in the metals as occluded matter such as deeply imbedded nickel oxide and carbon may easily escape detection by other methods, one of which is spectroscopic analysis.

A primary object of the present invention is to provide a method of testing for occluded matter in metals which is comparatively rapid and relatively simple.

A further object of this invention is to provide a method for determining the presence of occluded impurities in metals by atomic hydrogen bombardment.

A still further object of this invention is to provide a system of simple construction for the testing for the presence of occluded matter in metals.

Another object of the present invention is to provide a system for the testing for the presence of occluded matter in metals by means of atomic hydrogen bombardment.

These and other objects will be apparent from the following specification when taken in connection with the accompanying drawing, in which:

The figure is a schematic diagram of a complete system for testing for occluded matter in metals according to the principles of this invention.

In the following specification this invention will be disclosed using nickel as the metal containing the occluded impurities. As is well known to those skilled in the art it will also be applicable to other metals.

The method consists essentially of exposing a sample of nickel to atomic hydrogen, and then identifying the volatile gas formed, which is composed of hydrogen and the occluded impurities in the nickel.

Although the apparatus of this invention may be made in several forms, it i herein disclosed in the figure as a radio frequency power source I0 connected to two electrodes I and I2 by means of leads and 2|. Electrode H is a cylindrical electrode surrounding that portion of the glass bulb 13 which contains a solid cylinder of the nickel being tested. In practice glass bulb I3 i formed around the metallic sample to be tested in any conventional manner. The sample to be tested acts as an electrode I2 and is mounted on and electrically connected to a lead 20, this electrode being at ground potential. Glass bulb I3 is connected to a source of hydrogen [4 by means of tubing i5 and I6, and to a vacuum pump IT by means of tubes l6 and I8. Between the connecting point of tubes l5 and i5 and the hydrogen source I 4 is located a stopcock 19. Likewise between the connecting point of tubes [5 and i8 and a vacuum pump 57 is located a stopcock 22.

In the testing process the previously disclosed system is operated in accordance with the following procedure: A small cylinder of nickel I2 is mounted in a glass bulb 13 by means of an elec trode lead 20, which is fastened to one terminal of a radio frequency power source H3. The other terminal of the power source is connected to electrode H. The glass bulb containing the nickel cylinder is then heated in an oven (not shown) to approximately four hundred degrees (400") centigrade to drive ofi residual gases. The nickel cylinder is next heated by induction heating to approximately nine hundred degrees (900) centigrade and held at this temperature for at least one to two minutes. The glass bulb is then evacuated by means of vacuum pump [1 and sealed 01f by stopcock 22. Hydrogen from tank [4 is admitted to the glass bulb until it contains a. hydrogen filling at a pressure of .3 to .4 mm. mercury. Atomic hydrogen is then formed in the glass bulb by action of the radio frequency power source operating at a frequency of 6 megacycles per second and a voltage of four kilovolts. At intervals more hydrogen must be provided to replenish the hydrogen converted to atomic hydrogen and absorbed in the nickel cylinder, and subsequently reacting with the occluded impurities in the nickel. This procedure is continued for at least five to ten minutes. The glass bulb is then cooled to room temperature and fresh hydrogen admitted to replace the former filling. The glass bulb is then sealed off and heated by induction heating to nine hundred degrees (900) centigrade for two minutes. This heating drives oil? the newly formed volatile compounds, formed by the occluded nickel impurities and atomic hydrogen, into the glass bulb. These volatile impurities in the hydrogen gas filling of the bulb will give a characteristic color to the gas filling when excited by the radio frequency power source output. One skilled in the art can identify the occluded matter present by the characteristic color of the volatile gas present. The volatile aseous impurities could further and positively be identified by means of the spectograph, if such a method of identification should be found to be desirable.

While ape tiqu a f em mem iih n ntion has beenidispl ofsed and described, it is to be understood that various changes and modifications may be made therein without departing from the spirit and scope of the appended claims. 1

What is claimed is:

l. A method of testing a meta ljlic sample to v determine the presence d ssuaded-impurities which can react with atomicjiydrogen to Torin" a volatile compound which comprises, heating the sample in a vacuum to drive on residual gases,

enclosing said heated sample in a low pressure atmosphere of molecular hydrogen gasflonizing said gas to form atomic hydrogen, coolingsaid sample to room temperature While maintaining constant the pressure ofsaidniolecultir"hydrogen gas atmosphere, reheating said sample in said hydrogen gas "atmosphere, and applyin radio frequency power to cause an electric glow dis- 'charg'e'in said low -pressurehydrogenatmosphere.

2. A metho'dof testing anickel sample todetermine the presence of oxide'and carbon impurities which 'can'co'mbine with atomichydrogen to 'form 'a volatile compound which comprises the steps "of heating the sample 'in "an evacuated chamber to driveofl residual gases, admitting molecular hydrogengas 'into said chamber at "a predeterminedpressure while'heating said sampletoa'se'cond higher temperature, ionizing said mole'cularhydrogen gas to form atomic hydrogen, cooling's'aidsample to room temperature while maintaining constant the'pressureof-said molecular hydrogen gas,'reheatlng sai d' sample in said hydrogen atmosphere to'saidsecond temperature, and applying radio frequency power to cause anelectric glow discharge'insaid low pressure hydrogen atmosphere.

t3. Theunethod of testingametallic sample to determine 'the presence of occluded impurities -which. can react with atomic hydrogen "to form 'a volatile compound comprising, heating the sample 'inan evacuated chamber to'approximately 400 C. to drive off'residual-gases,*admitting molecular hydrogen gas to said chamber at a pressure at approximately 0.3'to'O'.-4'-millirneters of mercury while raising the temperature of said chamber to approximately 900 (2.;:applying radio frequency power to'ionize said mol'e'culan-gas'to form atomic hydrogenjor 'a time interval of five to ten minutes, cooling said sample'to, roomtemperature, admitting additional; molecular hydro- ,gen gastosald chamber to maintainapressure'of 0;3 to 0.4 millimetersof mercury, reheating said sample to; approximately 900 C ."to'drive'of'vo1atile ompon ds f atomic yd and pp y ne radio fjrequency'power to cause anelectric glow ischa se.. n. ai a m he 4. Themethodof testing 'a' nickel sample-to determine the presence of occluded oxide and car'- bon impurities which can combine with atomic hydrogen to form a volatile compound comprising, heating the sample in an evacuated chamber to approximately 400 C. to drive ofi residual gases, admitting molecular hydrogen gas to said chamber at a pressure at approximately 0.3 to 0.4 millimeters of mercury while raising the temperature of said chamber to approximately 900 C., applying radio frequency power to ionize said molecular hydrogen gas to form atomic hydrogen for a reaction period of five to ten minutes, adding hydrogen gas to hold pressure constant, coolsaid "sample to room temperature, admitting additional molecular hydrogen gas to said chambcijtbgnjalritairi'a pressure of 0.3 to 0.4 millimeters of mercury, reheating said sample to approximately-gqof Q. to drive oil volatile compounds of atomic hydrogen, and applying radio frequency powertd'cause an electric glow discharge in said atmosphere.

5. A- method for testing a metallic sample to determine the presence of occluded impurities other than hydrogen which can react with atomic hydrogen to form a volatile compound which comprises, heatingthe sample-in a'closed chamber to approximately 400 C. to-drive oif residual gases, thereafterraising the temperature to approximately 900 C. and evacuating the chamber, introducing molecular hydrogen gas to said chamber, applying radio frequency power to ionize the moleoular 'hydrogen-gas to-form atomic hydrogen, cooling the sample to room-temperature, addingfresh molecular hydrogengasto replace the hydrogen gas previouslyintroduced, reheating the sample toapproximately 900 C. to drive off volatile compounds of atomic hydrogen and occluded impurities and applying-radio frequencypow'er to cause an'electric glow discharge in the atmosphere surrounding the metallic sample.

L. YEATER.

RfrncsC itd in the file of this patent UNI TED STATES PATENTS "OTHER' REFERENCES Wooten Ind ;and ;Eng ;Chem., Anal) Ed. vol. 14, No. 10, pages 835-838, November 1942. L I liobalek Ind.';and Eng-Chem Anal. Ed.- vol. 17, N 9, pages 54 4 -53 ,"Septernber 194s. Stanley Ind. and Eng j Chem, A naL -Ed. vol. 17; No. 1 1, pa es 699-702, November 1945. 

1. A METHOD OF TESTING METALLIC SAMPLE TO DETERMINE THE PRESENCE OF OCCLUDED IMPURITIES WHICH CAN REACT WITH ATOMIC HYDROGEN TO FORM A VOLATILE COMPOUND WHICH COMPRISES, HEATING THE SAMPLE IN THE VACUUM TO DRIVE OFF RESIDUAL GASES, ENCLOSING SAID HEATED SAMPLE IN A LOW PRESSURE ATMOSPHERE OF MOLECULAR HYDROGEN GAS, IONIZING SAID GAS TO FORM ATOMIC HYDROGEN, COOLING SAID SAMPLE TO ROOM TEMPERATURE WHILE MAINTAINING CONSTANT THE PRESSURE OF SAID MOLECULAR HYDROGEN GAS ATMOSPHERE, REHEATING SAID SAMPLE IN SAID HYDROGEN GAS ATMOSPHERE, AND APPLYING RADIO FREQUENCY POWER TO CAUSE AN ELECTRIC GLOW DISCHARGE IN SAID LOW PRESSURE HYDROGEN ATMOSPHERE. 